Particle-In-Cell Simulation of Electron Acceleration in Solar Coronal Jets

TL;DR

This study combines MHD and particle-in-cell simulations to explore electron acceleration during solar coronal jets, revealing that electric fields in reconnection regions efficiently accelerate electrons to high energies.

Contribution

It introduces a novel multi-scale simulation approach linking MHD and PIC models to study electron acceleration in solar jets.

Findings

Electrons follow a power-law energy distribution with an index of -1.5.

Main acceleration driven by systematic electric fields in the reconnection current sheet.

Electron acceleration occurs rapidly, with electrons staying in the current sheet for only a few seconds.

Abstract

We investigate electron acceleration resulting from 3D magnetic reconnection between an emerging, twisted magnetic flux rope and a pre-existing weak, open magnetic field. We first follow the rise of an unstable, twisted flux tube with a resistive MHD simulation where the numerical resolution is enhanced by using fixed mesh refinement. As in previous MHD investigations of similar situations, the rise of the flux tube into the pre-existing inclined coronal magnetic field results in the formation of a solar coronal jet. A snapshot of the MHD model is then used as an initial and boundary condition for a particle-in-cell simulation, using up to half a billion cells and over 20 billion charged particles. Particle acceleration occurs mainly in the reconnection current sheet, with accelerated electrons displaying a power law in the energy probability distribution with an index of around -1.5. The main acceleration mechanism is a systematic electric field, striving to maintaining the electric current in the current sheet against losses caused by electrons not being able to stay in the current sheet for more than a few seconds at a time.